Carburetor choking device



June 27, 1967 WINKLER ETAL 3,328,011

CARBURETOR CHOKING DEVICE Filed Nov. 5, 1965 '3 Sheets-Sheet 1 ALBERT H. WINKLER DONALD F. MORGAN WALTON B. BALDWIN.

IN VENTORS A TTORNEY June 1967 A. H. WINKLER ETAL 3,323,011

CARBURETOR CHOKING DEVICE 5 Sheets-Sheet 2 Filed Nov. 5, 196

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United States Patent O 3,328,611 CARBURETOR CHOKING DEVICE Albert H. Winkler and Walton B. Baldwin, Elmira, and Donald F. Morgan, Horseheads, N.Y., assignors to The Bendix Corporation, a corporation of Delaware Filed Nov. 3, 1965, Ser. No. 506,226 3 Claims. (Cl. 26139) The present invention relates to a choking device for a carburetor for an internal combustion engine. More particularly, the present invention relates to a novel interconnection of the choke shaft and the choke valve for significantly improving cold engine performance.

Prior art automatic choking devices for internal combustion engines using bimetal thermostats, offset (unbalanced) choke valves, mechanically operated choke valve crackers and manifold vacuum motors failed to provide a sufficiently rich mixture immediately after starting a cold engine to eliminate engine stall immediately following the start, as the engine is shifted into gear, or engine pass out or sputter on first acceleration after a cold start or all conditions. At the same time, prior art carburetors with bimetal thermostats and manifold vacuum motors provided an increasingly rich mixture as engine speed increased. The increasingly rich mixture was unnecessary for proper engine operation and was therefore uneconomical.

It is an object of the present invention to eliminate engine stall after the first cold start and succeeding cold starts.

It is an object of the present invention to eliminate engine fade out or stutter on the first and succeeding cold engine acceleration.

. It is an object of the present invention to increase cold engine fuel economy.

It is an object of the present invention to improve the performance of prior art chokes using bimetal thermostats and vacuum motors by enriching the fuel-air mixture at low engine speeds and leaning the fuel-air mixture at higher engine speeds.

It is a further object of the present invention to provide a simple, inexpensive, reliable and rugged automatic choke device which can be readily used with existing carburetors.

It is a further object of the present invention to provide a novel automatic choking device which will enrich the fuel-air ratio at cold engine fast idle speed.

It is a still further object of the present invention to provide a mechanism to improve the performance of prior art automatic chokes using mechanically-operated choke crackers or vacuum motors and bimetal thermostats which is more responsive to air flow on the ofiset choke valve.

It is a still further object of the present invention to provide a novel automatic choking device which has no effect on warm engine operation.

It is a still further object of the present invention to provide a novel choking device having relative motion between the choke valve and the choke shaft in which the choke valve is held during engine cranking operation in a fully closed position.

Additional objects and advantages of the present invention will be apparent from the detailed description which follows in conjunction with the accompanying drawing wherein one embodiment of the present invention is illustrated.

The following description is taken in connection with the accompanying drawing in which:

FIGURE 1 is a side elevational view of a carburetor being an embodiment of the present invention showing the air horn, main body, and the throttle body;

FIGURE 2 is a sectional view of the air horn shown in 3,328,01 l Patented June 27, 1967 "ice FIGURE 1 and an embodiment of the present invention in position prior to energization of the starting motor of a cold engine;

FIGURE 3 is a view similar to FIGURE 2 in which the embodiment of the present invention is shown in the vacuum kick position;

FIGURE 4 is a view similar to FIGURES 2 and 3 in which the embodiment of the present invention is shown in open throttle operation; and- FIGURE 5 is a graph comparing the performance of identical carburetors, one with an embodiment of the present invention and one without.

Turning now to FIGURE 1, an automatic choking type carburetor, generally designated by numeral 10, has an air born 12, a main body 14, and a throttle body 16. A vacuum motor, shown generally by the numeral 18, has a spring member 20, a diaphragm 22, a vacuum line 24, and a case 26 which is vented at 28 to maintain one side of the diaphragm at atmospheric pressure. The vacuum line is connected to a source of manifold vacuum (not shown). The diaphragm 22 is connected to a shaft 30 which is journalled on the case 26 and connected to an arm 32. The arm 32 is connected to a slotted disc 34 which is connected to the choke shaft 50, journalled through the air born 12. A thermostatically-controlled element, shown generally by the numeral '35, has a bimetallic spring 39 fixedly connected at one end and free to rotate at the other end against an arm 38 which is connected to rod 41. The rod 41 is connected by a fastening member 42 to the slotted disc 34 so that slotted disc will rotate in response to the rotation of the arm 38. The operation and construction of the thermostaticallycontrolled element and the vacuum motor are well known in the art. The construction illustrated of the vacuum motor and thermostat is an example of the structures which may be employed in conjunction with the present invention.

Turning now to FIGURES 2, 3 and 4, the air born 12 has an induction passage 40 formed therein. A choke shaft 50 is eccentrically journalled for rotation through the induction passage. A bracket or arm 52 is fixedly connected to the rod or choke shaft 50 by a rivet 54 or any other convenient method. The bracket or arm 52 has first and second extending members or fingers 56 and 58. An olfset choke valve 60 is connected to the choke shaft 50 to permit relative angular displacement or relative rotation between the choke shaft and the choke plate. The choke valve is of the well-known butterfly valve type. having a minor portion extending to the left of shaft 50, FIGURE 2, and a major portion extending to the right, comprising one unitary rigid offset valve member. A link or rod member 62 is fitted through the choke valve 60 and the first extending member or finger 56 of the arm or bracket 52. The link 62 has abutments or stops 64 and 66 formed on its transverse ends to limit the maximum angular or rotational displacement of the choke plate and choke shaft relative to one another. A helical coil spring member 68 is disposed about the link 62 intermediate of the choke valve 60 and the choke arm 52. The axial dimension of the coil spring 68 is usually greater than the length of the link 62. The second extending member or finger 58 of the arm 52 is closer to the choke plate than the first finger 56 and is positioned to limit the minimum angular or rotational displacement of the choke plate relative to the choke shaft. 4

In operation, the present invention acts as follows. If the engine to be started were at 0 Fahrenheit, the thermostatic motor 35 is adjusted to rotate the disc and choke shaft in the direction shown by the arrow 70 and to position the choke valve 60 and the choke arm 52 as shown in FIGURE 2. The second finger 58 is operative during engine cranking to fully close the choke plate 60 in the induction passage 40 such that air flows in the passage are not able to open the choke valve 60 until sufficient pressure differential is established above and below the offset choke valve to overcome the closing force of the thermostat. The starter motor (not shown) is engaged and the engine cranked. Once the engine fires, the vacuum motor 18, which senses manifold vacuum, operates to draw the diaphragm inwardly, compressing spring 20, thereby rotating the slotted disc 34 of the choke shaft in the direction shown by the arrow 72 which positions the choke arm and choke valve approximately as shown in FIGURE 3. This position is known as the vacuum kick position. Frequently, when a cold engine is started, the throttle valve (not shown) is opened slightly by the engine operator. Once the engine starts with slightly-opened throttle, a slightly larger air flow than fast idle is present. This air flow acts on the unbalanced offset choke valve 60 to rotate it slightly in the position shown in FIGURE 3. If the operator releases the throttle valve, the engine will operate under its own cold engine fast idle system (not shown). Fast idle devices connected relative to the choke shaft are well known in the art. See for example, US. Patent 2,420,917 issued to Sutton and Winkler wherein a fast idle cam and fast idle set screw are used to control idle speed in response to choke shaft position. It is expected that similar devices attaining similar objectives will be used in connection with the present invention. The reduced air flow on the offset choke valve will enable the spring 68 to rotate the choke plate in the direction shown by arrow 74 in a more closed direction. As the operator opens the throttle valve past the cold engine fast idle speed range, greater air flow past the offset choke plate 60 causes the offset choke valve 60 to be rotated against the spring 68 in the direction shown by arrow 76. The effect of rotation of the choke plate 60 in the direction shown by arrow 74 is to enrich the fuel-air mixture at the cold engine fast idle point. Rotation of the choke plate in the direction shown by arrow 76 leans the fuel-air mixture at engine speed above the cold engine fast idle point. At a predetermined engine speed, the offset choke valve 60 is opened by air flow on its unbalanced surface to the point that it is in contact with the second finger member 58. The choke valve 60 and choke bracket 52 are then in the position shown in FIGURE 4. The choke valve 60 is held against the second finger 58 of the choke arm 52 by the air flow acting on the unbalanced or offset choke valve. Further increases in engine speed require the increased air flow on the oflset choke plate to act against the thermostatic motor spring.

Prior art automatic chokes used a stiff or heavy himetal spring in order to close the choke valve completely for quick, sure starting over a wide range of ambient temperature. The ambient temperature biased or preloaded the stiff or heavy thermostat spring. Such a biased stiif or heavy spring was not responsive to small changes in air flow on the offset choke valve. To partially open the choke valve and allow a leaner mixture after an engine start was obtained, a vacuum motor or a mechanic-a1 linkage between the throttle mechanism and choke mechanism was added to prior art devices. This addition made the fast idle range mixture too lean and the higher than fast idle mixture too rich because of the still present effects of the too rigid biased thermostat spring. The present invention, 'by using a lighter, relatively-unbiased spring intermediate of the high force rigid thermostat spring and the air flow forces on the unbalanced choke valve in cooperation with the choke cracking devices enriches the fast idle range mixture to eliminate stalling and engine fade out and leans out the mixture above fast idle range for greater fuel economy. These effects are well shown by FIGURES 2, 3 and 4. Past the operating point, shown in FIGURE 4, the effects of the light intermediate spring 68 is gradually allowed to decrease in order to enrich the more wide open throttle mixture.

The effects of the present invention on the engine fuelair mixture ratio can be seen in the graph shown in FIG- URE 5 which the mixture ratio in pounds of fuel per pounds of air is shown on the vertical axis and the air flow in pounds per hour (which corresponds to engine speed and generally to vehicle speed) is plotted on the horizontal axis. In FIGURE 5, curve is that of an automobile bimetal thermostat and vacuum motor carburetor employing the present invention and curve 84 is that of the same carburetor without the present invention. Curve 86 shows the mixture ratio plotted against air flow for an engine at normal engine operating temperature. Curves 80 and 84 are plotted for 0 Fahrenheit engine temperatures.

It can be easily seen that the present invention causes a significantly richer fuel-air mixture at the cold engine fast idle range (65 to 75 pounds per hour for the engines used in the present test). This richer mixture is caused by the spring 68 forcing the choke plate in a closed direction, shown by arrow 74 in FIGURE 3, when the vacuum motor positions the choke plate in the vacuum kick position. As air flow increased corresponding to increased engine speed, the fuel-air mixture leans out quickly due to the effect of air flow on the unbalanced choke plate 60 which acts against the spring 68 to rotate the choke plate 60 in the direction shown by arrow 76 in FIGURE 3. Over the air flow range of about pounds per hour to about 660 pounds per hour, the present invention provides a leaner fuel-air mixture than prior art automatic chokes. This range covers substantially all of the city traflic driving range and all of the suburban and highway driving range. Examination of the graphs indicates that the cold engine f-ast idle mixture of the present invention is significantly higher than that of prior art carburetor choking devices. The cold engine fast idle mixture ratio of prior art devices is not appreciably richer than the mixture ratio of a warm engine at idle.

It can thus be seen that the present invention attains its stated objectives. A richer mixture is provided at cold engine fast idle to prevent engine'starting and pass out or stutter at first acceleration; yet a leaner mixture is provided at most driving speeds above cold engine fast idle for increased warm up economy. The comparison shown by the graph of FIGURE 5 demonstrates the superiority of the present invention over prior art automatic choke carburetors. Further, the present invention, as can be readily seen by the structure described, is simple, sturdy, inexpensive and unlikely to malfunction. The second finger member 58 is operative to keep the choke plate 60 fully closed in the induction passage 40 during engine cranking operation if the thermostat closing force is suflicient to fully close the choke valve. The link ends prevent the excessive separation of the choke valve 60 and the bracket 52 which would cause the spring 68 to fall off as well as defining maximum angular displacement between the choke plate 60 and choke shaft 50.

Although certain structures have been shown and described in detail, it will be understood that changes may be made in the design and arrangement of parts without departing from the spirit of the invention.

We claim:

1. In an automatic choking device for an internal combustion engine carburetor having an air horn with an induction passage therethrough, a rotatable choke shaft journalled through the air horn, an offset rigid butterfly choke valve, a temperature responsive means and a pressure responsive means:

first and second finger members fixedly connected to the choke shaft;

a link member interconnecting the butterfly choke valve and the first finger member adapted to limit the maximum relative angular displacement of the choke shaft and the butterfly choke valve;

the second finger member adapted to limit the minimum angular displacement of the choke shaft and the butterfly choke valve; and

resilient means intermediate of the first finger member and the butterfly choke valve operative to control the rotation of the butterfly choke valve relative to the first and second finger members such that the butterfly choke valve is rotated in a closed direction at and below a specified low engine speed and rotated in an open direction above a specified low engine speed.

2. In an automatic choking device for an internal combustion engine carburetor having an air horn with an induction passage therethrough, a rotatable choke shaft journalled through the air horn, an offset rigid butterfly choke valve, a temperature responsive means and a choke opening means for positioning the choke following a cold start:

first and second finger members fixedly connected to the choke shaft;

a link member interconnecting the butterfly choke valve and the first finger member adapted to limit the maximum relative angular displacement of the choke shaft and the butterfly choke valve;

the second finger member adapted to limit the minimum angular displacement the choke shaft and the butterfly choke valve; and

resilient means intermediate of the first finger member and the butterfly choke valve operative to control the rotation of the choke relative to the first and second finger members such that the butterfly choke valve is rotated in a closed direction at and below a specified low engine speed and rotated in an open direction above a specified low engine speed.

3. In an automatic choking device for an internal combustion engine carburetor having an air born with an induction passage therethrough, a rotatable choke shaft journalled through the air horn, an offset rigid 6 butterfly choke valve, a temperature responsive means and a pressure responsive means:

the rigid butterfly choke valve controlled by the temperature responsive means and the pressure responsive means to be maintained in a partially-open vacuum kick position during engine cold idle operation;

an arm means connected to the choke shaft for rotation with the choke shaft;

the butterfly choke valve connected to the choke shaft for rotation relative to the choke shaft;

said arm means having first and second extending members, the first member spaced further from the butterfly choke valve than the second member, said second member operative to limit the rotation of said butterfly choke valve relative to said choke shaft in one direction of rotation;

linking means including a rod member having means on each end thereof adapted to engage respectively the first extending member and the butterfly choke valve to limit rotation of said butterfly choke valve relative to said choke shaft in the other direction of rotation; and

spring means including a coil disposed about said rod member to bias said butterfly choke valve towards said other direction of rotation.

References Cited UNITED STATES PATENTS Re. 22,840 2/ 1947 Jorgensen 26139 1,955,204 4/1934 Sawyer 123-119 2,421,733 6/1947 Henning 26139 X 2,998,233 8/1961 Marsee 261-39 3,227,428 1/ 1966 Charron 26139 FRANK W. LUTTER, Primary Examiner.

HARRY B. THORNTON, Examiner.

T. R. MILES, Assistant Examiner. 

1. IN AN AUTOMATIC CHOKING DEVICE FOR AN INTERNAL COMBUSTION ENGINE CARBURETOR HAVING AN AIR HORN WITH AN INDUCTION PASSAGE THERETHROUGH, A ROTATABLE CHOKE SHAFT JOURNALLED THROUGH THE AIR HORN, AN OFFSET RIGID BUTTERFLY CHOKE VALVE, A TEMPERATURE RESPONSIVE MEANS AND A PRESSURE RESPONSIVE MEANS: FIRST AND SECOND FINGER MEMBERS FIXEDLY CONNECTED TO THE CHOKE SHAFT; A LINK MEMBER INTERCONNECTING THE BUTTERFLY CHOKE VALVE AND THE FIRST FINGER MEMBER ADAPTED TO LIMIT THE MAXIMUM RELATIVE ANGULAR DISPLACEMENT OF THE CHOKE SHAFT AND THE BUTTERFLY CHOKE VALVE; THE SECOND FINGER MEMBER ADAPTED TO LIMIT THE MINIMUM ANGULAR DISPLACEMENT OF THE CHOKE SHAFT AND THE BUTTERFLY CHOKE VALVE; AND RESILIENT MEANS INTERMEDIATE OF THE FIRST FINGER MEMBER AND THE BUTTERFLY CHOKE VALVE OPERATIVE TO CONTROL THE ROTATION OF THE BUTTERFLY CHOKE VALVE RELATIVE TO THE FIRST AND SECOND FINGER MEMBERS SUCH THAT THE BUTTERFLY CHOKE VALVE IS ROTATED IN A CLOSED DIRECTION AT AND BELOW A SPECIFIED LOW ENGINE SPEED AND ROTATED IN AN OPEN DIRECTION ABOVE A SPECIFIED LOW ENGINE SPEED. 